Vegan eggs can be formulated by one plant-based ingredient or a combination of ingredients to recreate the functionality of eggs.
Pulses are ingredients rich in proteins, starches, and fibers, as well several health beneficial ingredients
[12]. Proteins deriving from pea, lentil, lupine, and chickpea can confer in their native and modified forms interesting functionalities, such as gelling, emulsification, and foaming for formulating vegan eggs
[13][14][15][16]. These proteins can be used in different forms, namely flours, protein concentrate, or isolates. Besides their high nutritional value, pulses are known for their affordability and sustainability
[12]. Furthermore, pulses are recognizable products by the consumers, and their inclusion in vegan egg formulations might contribute to their acceptability. The proteins of pulses have plenty of pros, but they have some nutritional limitations, such as their low content in sulfur amino acids, which can be overcome by blending them with cereals. Also, plant proteins have a globular structure that impacts the functionality and, more specifically, the solubility. To overcome such concerns, the addition of hydrocolloids was suggested to improve the functionality of proteins
[17][18]. As an alternative, these proteins can be improved by postprocessing using thermal treatments, fermentation, and crosslinking by means of enzymes to improve the emulsification, gelling, and foaming abilities
[19][20][21]. Pulses also present flavors described as “beany” or “green”, attributed to their content in saponins, ketones, and aldehyde compounds
[22]. Several solutions are being applied to attenuate these flavors, such as using masking agents and mitigation processing
[23][24]. Starches from pulses are also increasingly used in formulating vegan eggs to play the role of binding and thickening
[25]. Native starches from pulses have some functional limitations compared to those usually used, such as tapioca and corn starches
[26][27]. Nevertheless, several postprocessing methods are being developed to produce modified starch with high quality, likely-modified pea starch
[28][29]. Another ingredient, aquafaba, derived from cooked chickpea, is gaining interest as an egg substitute due to its foaming, emulsifying, thickening, and gelling properties
[30][31][32]. This is attributed to its composition, namely protein, water-soluble/insoluble carbohydrates, coacervates, saponins, and phenolic compounds
[22][33]. The main limitation for the commercialization of aquafaba is the lack of product standardization due to the high variability in chickpea properties (differences in the composition and genotypes) and processing conditions (temperature, pressure, and cooking time)
[34][35][36][37]. Different types of hydrocolloids, such as carrageenan, pectin, and guar gum, have been used as natural foaming, thickening, and emulsifier agents to further reinforce the structure made by plant-based proteins and starches, and for an improved mouthfeel
[38][39][40]. Fibers from pulses are also of relevance in vegan egg formulations due to their gelling, binding, and thickening properties. Nevertheless, the most used fibers derive from apple, citrus, and oat fibers. Cellulose derivatives, such as carboxymethyl cellulose or hydroxypropyl methylcellulose, can be used as thickeners or emulsifiers.
Oilseeds (mainly soybeans) are also used in different forms, such as proteins, flour, or milk, owing to their high protein content, complete essential amino acids, and protein digestibility that can be comparable to that of animal proteins
[41]. In recent years, consumers have been concerned about soy ingredients for their genetically modified reputation and allergenicity
[42][43]. This has given room for more emerging sources, such as oat, mung bean, lentil, and faba bean
[44][45][46].
Emerging ingredients, such as algal flours, are also of interest as food ingredients due to their high nutritional quality and sustainability
[47]. They are a rich source of proteins, lipids, fibers, and vitamins
[48]. Compared to plant ingredients, algae are also a good source of vitamin B12 for vegetarians and vegans
[49]. They also contain functional ingredients, such as monoglycerides, diglycerides, and phospholipids, mainly acting as emulsifiers
[41][50]. Indeed, the first vegan egg (VeganEgg) using algal flours was launched in 2017.
Vegetable oils, such as canola and sunflower oils, are also important as structuring agents in vegan egg formulations, hence contributing to the creation of the textural attributes, flavor profile, and mouthfeel of the final products
[30]. Flavoring agents such as Himalayan black salt or “Kala namak” are commercially available to mimic the sulfur flavor of egg
[51]. Other ingredients can be added, such as spices (e.g., garlic powder, sugar, and salt), buffers (e.g., bicarbonates or phosphates), and preservatives (e.g., nisin)
[52].